1. Field of the Invention
The present invention relates to a color cathode-ray tube and, more particularly, to a color cathode-ray tube in which a half etching line is formed surrounding the effective area of a shadow mask in order to increase curved surface supporting strength of the shadow mask to allow the shadow mask to endure shocks.
2. Description of the Related Art
A conventional color cathode-ray tube is described below with reference to FIG. 1. The conventional color cathode-ray tube is constructed in a manner that a front glass called a panel 1 and a back glass called a funnel 2 are combined with each other through a frit glass. The cathode-ray tube includes a fluorescent plane 4 emitting light, formed on the inner surface of the panel, an electron gun 14 serving as a source of electron beams (6) for making the fluorescent plane 4 generate light, a shadow mask 3 for selecting colors to allow a predetermined fluorescent substance to emit light, and a frame 7 for supporting the shadow mask 3. A spring 8 for combining the frame with a stud pin of the panel 1 is attached to the frame. An inner shield 9 for shielding the cathode-ray tube to allow it not to severely affect by external magnetic field during its operation is also attached to the frame.
In the operation of the color cathode-ray tube, the electron beams 6 emitted from the electron gun 14 set inside a neck 15 of the funnel 2 strike the fluorescent plane 4 formed on the inner face of the panel 1 according to a positive voltage applied to the cathode-ray tube. Here, the electron beams 6 are deflected by a deflection yoke 5 upward, downward, left and right before reaching the fluorescent plane, to form an image. There is a magnet 10 with a 2-pole, 4-pole or 6-pole for correcting the traveling path of the electron beams 6 to allow them to accurately strike a predetermined portion of the fluorescent plane, which prevents color purity from being deteriorated.
The general cathode-ray tube may be easily exploded due to an external shock because it has a high degree of vacuum state therein. To prevent this, a reinforcing band 11 is attached to the skirt of the panel 1 to disperse the stress of the cathode-ray tube with the high-level vacuum state to secure shock-resistance.
In the general cathode-ray tube, however, red, green and blue electron beams that have passed through electron beam passage holes of the shadow mask are needed to be exactly landed on the three-color fluorescent plane in order to display images with high resolution on a fluorescent screen. This also requires that a gap (q-value) between the inner side of an effective area of the panel and an effective area of the shadow mask be maintained within a predetermined acceptance range.
For recent color cathode-ray tubes, flat panels have been proposed in order to improve visibility. One type of flat panel cathode-ray tube is shown in FIG. 2, with reference to the same reference numbers illustrated in FIG. 1. This flat panel has the outer surface that is also flat and the inner surface having curvature smaller than that of the effective area of the conventional color cathode-ray tube. This requires the shadow mask applied to the color cathode-ray tube having the panel whose effective area is flat to have smaller curvature, resulting in a decrease in curved surface supporting strength of the effective area of the shadow mask. In general, the shadow mask for the color cathode-ray tube is partially deformed when it has a shock above a predetermined strength, deteriorating color purity.
It is, therefore, an object of the present invention to provide a color cathode-ray tube for increasing the curved surface supporting strength of the shadow mask and mitigating shocks applied to the shadow mask, to prevent deterioration of color purity.
To accomplish the object of the present invention, there is provided a color cathode-ray tube comprising a panel having a fluorescent plane formed on the inner surface thereof, and a shadow mask arranged at the inner side of the panel, having a predetermined distance therefrom, in which the shadow mask has an effective area in which electron beam passage holes are formed and a non-effective area surrounding the effective area, and at least one half etching line is formed at the non-effective area of the shadow mask.
The half etching line may be formed to be extended toward at least one of the shorter side and longer side of the shadow mask, or formed between a bent portion and a portion attached to the frame at the skirt of the shadow mask.
The half etching line may be formed on each of both sides of the non-effective area. In this case, it is preferable that the half etching lines are alternately formed on both sides of the non-effective area.
The half etching line has a rectangular shape surrounding the effective area. The radius of curvature of the corner of the half etching line is 0.8-3 mm, preferably.
The half etching line is preferably applied to a shadow mask of a flat color cathode-ray tube, whose outer surface is substantially flat and whose inner surface has predetermined curvature.
It is preferable that the distance between the effective area and the half etching lines corresponds to 100-200 xcexcm, the width of the half etching line is 50-100 xcexcm, there are at least two half etch lines, the distance between the two half etching lines corresponding to 100-150 xcexcm, and the etched depth of the half etching line corresponds to 15-45 xcexcm.